RegEx Question for Strong Password

Question

RegEx Question for Strong Password

Jassim Al Rahma 1,616

Hi,

I need help with this RegEx please.

I want to have a strong password with the following:

Minimum 8 characters, Maximum 15
Must Start with Alpha
Must have mixed Alpha-Numeric
Can have capital and small Anywhere and no necessary in the beginning [but not must]
Can have special characters [but not must]

Kindly help..

Thanks,
Jassim

Accepted answer

2 additional answers

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Answer 1

Viorel 122.5K

Based on new details, try another expression:

(?i)^(?=[a-z])(?=.*[0-9])([a-z0-9!@#$%\^&*()_?+\-=]){8,15}$

Gary Nebbett 6,216 Reputation points

2021-04-12T19:25:54.813+00:00

Hello @Viorel ,

This is really nit-picking of me (especially since the Unicode value of '=' is less than that of '\'), but you have placed the '-' not at one of the ends of the character group. This could have led to unintended consequences...

Gary
Viorel 122.5K Reputation points

2021-04-12T19:34:12.197+00:00

Since ‘-‘ is preceded by ‘\’, it is a simple ‘-‘, not a range of characters.
Jassim Al Rahma 1,616 Reputation points

2021-04-12T19:44:30.71+00:00

It shows an error
Viorel 122.5K Reputation points

2021-04-12T19:45:59.507+00:00

The expression was made for C# (Regex class), not for JavaScript.
Gary Nebbett 6,216 Reputation points

2021-04-12T20:05:21.743+00:00
Hello @Viorel ,

Sorry to bother you again, but are you sure? Is it not the case that restricted escaping rules apply in positive character groups?

I just made these tests to confirm (my possibly tired and unreliable) expectations:

Console.WriteLine(Regex.IsMatch(@"[\t]", @"\t")); Console.WriteLine(Regex.IsMatch(@"[\t]", @"t")); Console.WriteLine((int)@"\t"[0]); Console.WriteLine((int)"\t"[0]);

with the results:

False True 92 9

I.e.

a tab does not match the positive character group [\t]

a "t" does match [\t]

Gary
Viorel 122.5K Reputation points

2021-04-12T20:20:21.74+00:00
Try this test too:

Console.WriteLine( Regex.IsMatch( "\t", @"[\t]" ) );
Jassim Al Rahma 1,616 Reputation points

2021-06-17T19:11:19.1+00:00
Hi

I used this:

^(?i)^(?=[a-z])(?=.*[0-9])([a-z0-9!@#$%\^&*()_?+\-=]){8,25}$

but having a lot of problems with users

How can I change to:

Must be 8-25 characters

Must have alpha+numeric or alpha+special character or numeric+special characters or alpha+numeric+special characters

alpha, numeric and special characters can be any anywhere: beginning or middle or end

can be all Upper, all Lower or mixed.

There is no minimum or maximum number for the alpha, numeric, and the special characters so it can have 8 special characters and one number only for example.

Thanks,
Jassim

Answer 2

Viorel 122.5K

Check this expression:

^(?=.{8,15}$)(?=\p{L})(?=.*\p{N}.*$).*

If it does not work, or "special character" means something specific, then show the code and sample passwords.

Jassim Al Rahma 1,616 Reputation points

2021-04-12T14:11:41.94+00:00
or "special character" means something specific

Just the standard special characters, !, @, #, $, %, ^, &,*, (, ), _, ?, +, -, =

Forgot to mention No Space

Here are sample of valid passwords:

unitedstates2020

unitedstates@#2020

uNiTedStAtEs2020=

United2020States%

here are sample of invalid passwords

United [less than 8]

United@#States?&2020 [more than 15]

United!@ States [it has a space]

UnitedStates [ No numeric]

2020UnitedStates [starting with numeric]

Answer 3

Hello @Viorel ,

Oops! Sorry, Mea culpa, I got the order of the input and pattern arguments wrong.

This is a bit off-topic but possibly still relevant for @Jassim Al Rahma to create a bullet-proof regular expression.

I am now having difficulty identifying a definitive source of information for this topic. The .NET documentation says:

The following table lists the character escapes supported by regular expressions in .NET.

CHARACTER ESCAPES IN .NET
Character or sequence Description
All characters except for the following:

. $ ^ { [ ( | ) * + ? \ Characters other than those listed in the Character or sequence column have no special meaning in regular expressions; they match themselves.

The characters included in the Character or sequence column are special regular expression language elements. To match them in a regular expression, they must be escaped or included in a positive character group. For example, the regular expression \$\d+ or [$]\d+ matches "$1200".

Wikipedia says (in the "POSIX basic and extended" section):

A bracket expression. Matches a single character that is contained within the brackets. For example, [abc] matches "a", "b", or "c". [a-z] specifies a range which matches any lowercase letter from "a" to "z". These forms can be mixed: [abcx-z] matches "a", "b", "c", "x", "y", or "z", as does [a-cx-z].
The - character is treated as a literal character if it is the last or the first (after the ^, if present) character within the brackets: [abc-], [-abc]. Note that backslash escapes are not allowed. The ] character can be included in a bracket expression if it is the first (after the ^) character: []abc].

Gary

P.S.

I also just found this: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05

A bracket expression (an expression enclosed in square brackets, "[]" ) is an RE that shall match a specific set of single characters, and may match a specific set of multi-character collating elements, based on the non-empty set of list expressions contained in the bracket expression.

The following rules and definitions apply to bracket expressions:

A bracket expression is either a matching list expression or a non-matching list expression. It consists of one or more expressions: ordinary characters, collating elements, collating symbols, equivalence classes, character classes, or range expressions. The <right-square-bracket> ( ']' ) shall lose its special meaning and represent itself in a bracket expression if it occurs first in the list (after an initial <circumflex> ( '^' ), if any). Otherwise, it shall terminate the bracket expression, unless it appears in a collating symbol (such as "[.].]" ) or is the ending <right-square-bracket> for a collating symbol, equivalence class, or character class. The special characters '.', '*', '[', and '\' ( <period>, <asterisk>, <left-square-bracket>, and <backslash>, respectively) shall lose their special meaning within a bracket expression.

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RegEx Question for Strong Password

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